SRB2 has only officially supported 44.1kHz audio for both music and sound for a long time. However, the sound backend used in the win32 interface (old srb2win, srb2dd) would resample sound automatically if it did not fit the requirements, as that was a feature of fmod.

Unfortunately, the SDL2 interface is not capable of resampling audio as before. In order for your sounds to play back correctly, it must be sampled at 44.1kHz. If you have staticy or otherwise broken sounds, it is not sampled at 44100 or 22050. Please use your audio encoding tools to encode your sound effects at that sampling rate.

For custom music, which does not have the same restraints as sound effects, looping with LOOPPOINT will not work unless the song is at 44.1kHz. Looping with LOOPMS works as before. This is a caveat of SDL_mixer that does not allow us to detect the sampling frequency of the music being used.

In srb2dd, sound and music work the same as they did before, however we are starting to phase out support for the old win32 code as it is not holding up well in recent versions of Windows.

when I imported the file (says it has a bitrate of 161 on the file's info) Audacity though it was at the correct rate already apparently. But after exporting it and then bringing it back into my project, it was still too fast. As if nothing was changed (most likely nothing was.)

You could try changing the bitrate manually from the track window itself (there's a tiny arrow near its name), and then re-adjusting its speed by multiplying it with (old rate)/44100 with the Change Speed option.